BY MOLECULAR COALESCENCE. 49 
whilst, under the same circumstances, and where the 
chemical action had the same amount of activity, these 
would always be the same, there ought to be a corre- 
sponding difference in the shapes and the sizes of different 
primitive crystals, agreeing with the uniformity, or want 
of uniformity, of the conditions under which these crystals 
ave formed. After these first crystals are thus produced, 
they will become grouped together and built up by the 
action of gravity into other forms depending upon the 
order and manner in which they are packed together. 
But, as this belongs exclusively to the subject of crystal- 
lography, I shall not enter systematically into it. There 
is, however, room for another observation connected 
with this part of the subject. It may be asked by 
what the primitive atoms or molecules are prevented from 
coming into absolute contact after the cessation of the 
chemical action, and the consequent evolution of fresh 
portions of electricity. It is not improbable or incon- 
sistent with the facts of electrical isolation, that these 
molecules should be sufficiently isolated to retain their 
state of electricity, and therefore continue, after the 
subsidence of the chemical action, to repel one another. 
However this may be, it is certain that there is one agent 
of universal existence as a repelling force, namely, caloric, 
which will prevent in these instances the absolute contact 
of molecules. But how far caloric is rightly to be regarded 
as a distinct force, or only as one of the sensible effects of 
the same agency as electricity, it is not necessary here to 
consider, as it is only the fact of its separating or repulsive 
power which is insisted on. I may observe that the 
simple rectilinear forms shown in diagram, page 47, into 
which the molecules of adjacent groups are supposed to be 
thrown by the impulsive forces acting according to the 
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